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Anisotropic water diffusion in macroscopically oriented lipid bilayers studied by pulsed magnetic field gradient NMR
Pär Wästerby1, Greger Orädd, Göran Lindblom
1Department of Biophysical Chemistry, Umeå University, SE-90187, Umeå, Sweden.
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|August 31, 2002
Summary
Water diffusion across lipid bilayers shows high anisotropy, with diffusion parallel to the membrane being at least 70 times greater than perpendicular diffusion. This highlights the membrane
Area of Science:
- Biophysics
- Membrane Biophysics
- Nuclear Magnetic Resonance
Background:
- Cell membranes regulate water transport.
- Understanding water diffusion is crucial for cell function.
- Phospholipid bilayers are model systems for cell membranes.
Purpose of the Study:
- To measure the anisotropy of water diffusion in dimyristoylphosphatidylcholine (DMPC) bilayers.
- To quantify the ratio of parallel to perpendicular diffusion coefficients (D(parallel)/D(perpendicular)).
Main Methods:
- Utilized pulsed magnetic field gradient (pfg) Nuclear Magnetic Resonance (NMR).
- Employed NMR imaging hardware to generate magnetic field gradients at various angles relative to aligned lipid bilayers.
- Measured translational diffusion of water as a function of gradient angle.
Main Results:
- Water diffusion coefficient showed strong angular dependence.
- The anisotropy ratio (D(parallel)/D(perpendicular)) was estimated to be at least 70.
- Accurate determination of D(perpendicular) was limited by its very small value.
Conclusions:
- Water permeability across lipid bilayers is relatively low.
- The observed anisotropy suggests significant barriers to perpendicular water movement.
- Instrumental limitations and potential membrane defects may influence results.